Water tube steam boiler



T H m D R S WATER TUBE STEAM BOILER Filed March 7, 1955 Patented Mar. 24, 1936 [TD STATES PATENT OFFICE WATER TUBE STEAM BOILER Application March 7, 1935, Serial No. 9,836 In Great Britain February 27, 1934 4 Claims.

. fuel employed in the installation.

The object of the present invention is to improve the circulation through the rows of tubes in or adjacent to the region of highest temperatures of the gases of combustion, so as to ensure that under conditions of forcing the boiler installation, undue heat stresses will not be set up in the tubes.

According to this invention the rows of tubes nearest the region of highest temperature, (these rows being generally the first 4 or 5 in large boiler installations) lead at their upper ends into a compartment in the upper drum the compartment being open at the top and of such height that it extends near to or above the normal working level of the water in the upper drum.

In a more limited form the invention consists in mounting in a substantially watertight manner on the inner face of the tube plate of the upper drum, a trough or compartment open at the top and of such height that it extends near to or above the normal water level in the drum, the bottom of the trough or compartment containing through its connection to the tube plate, the upper ends of those tubes which are nearest the region of highest temperature of the furnace, the upper ends of the remaining tubes being in communication with the Water space external to the compartment.

By employing the arrangement above set forth, steam, and any mixture of steam and water, rising through the more highly heated tubes, instead as hitherto of having to force a passage through the water in the drum, has to force its Way through a medium of less density contained in the watertight compartment, the medium under working conditions being steam or a frothy mixture of steam and water.

The compartment can be constituted by a pair of plates, running the length of the upper drum; or it may be built up in sections of suitable size for passing through the boiler manhole. The plates forming the longitudinal walls of the compartment are secured to the tube plate at their lower edges, and the compartment is completed by securing the plates at their ends to the ends of the drum, or by attaching end closing plates. The compartment may, if desired, be sub-divided by longitudinal or transverse partitions or both. The boiler feed water may be led to the water space surrounding the compartment in the upper drum or may be led into the lower drum or drums of the boiler.

If desired, deflecting plates can be mounted above the open top end of the compartment in order to deflect outwardly the uprising stream of steam and any water mixed with it, this having the effect of separating any water particles in the steam, which particles return to the water space surrounding the compartment.

Each lower drum can, if desired, be provided with an internal bafile or baffles forming with a portion of the usual tube plate, a compartment into which the lower ends of the more highly heated rows of tubes are led, the compartment being open at the lower end, the baffle or baffles being s-o arrange-d as to prevent any steam which may be mixed with the water coming down the less highly heated tubes acting as downcomers, from passing directly into the more highly heated rows of tubes.

By improving the circulation in the manner above stated, by the employment of the open-top, non-throttling compartment in the upper drum, with or Without reducing the possibility of steam entering the lower ends of the more highly heated rows of tubes by means of the battle or bafiles in the lower drum or drums, there is reduction in any tendency for steam pockets to be formed and retained in the more highly heated rows of tubes, thus any tendency for overheating, distortion or weakening of these tubes is very largely eliminated.

The provision for discharge from the more highly heated tubes into a trough or compartment which excludes the body of water in the upper drum reduces back pressure upon said discharge and thereby materially reduces the tendency for steam pockets to form in said tubes and insures a dense supply of fluid to the downoomer tubes of the boiler.

The accompanying drawing illustrates typical arrangements in accordance with the invention. Figure 1 shows a schematic end elevation of an installation comprising an upper drum and two lower drums. Figure 2 is a side elevation and Figure 3 a top plan View of the upper drum. Figure 4 is a schematic end elevation of an installation comprising one upper drum and one lower drum.

Referring now to Figures 1, 2, and 3, the upper drum l is provided with an internal watertight compartment 2, secured in any suitable way to the tube plate.' The lower end of the compartment communicates with the upper ends of the more highly heated rows of tubes 3, which usually will be up to about the first five rows, these being the tubes in the closest proximity to the position of highest temperature of the furnace. The compartment is open at the top and is closed at the ends by suitable end plates 2A. Alternatively the ends of the compartment may be fixed to the end plates of the drum. 7

The height of the compartment is arranged to be such that its open top is near to or above the normal working level of the water in the drum which water of course will be external to the compartment 2.

The compartment may be sub-divided by longitudinal or transverse partition plates which are numbered 4, 5 respectively.

The downcoming tubes 6 have their upper ends in communication with the water space I external to the compartment 2. The feed water may be supplied to the space I by tubes 8. Alternatively the feed water may be supplied to the lower drums, 9, 9. Each lower drum is provided with a baflle plate l0 secured to the tube plate and so positioned as to prevent immediate communication between the banks of tubes 3 and G. This baflie will prevent any steam that may be taken down by the tubes 6 into the lower drum, entering the more highly heated tubes 3.

Referring now to Figure 4 it will be observed that the construction illustrated follows generally the arrangement described with reference to Figures 1 to 3. It will be observed that the watertight compartment 2' in the upper drum I is of slightly different shape to that shown in Figures 1, v2, and 3. The most highly heated rows of tubes are numbered 3' and the less highly heated rows of tubes 6'. The feed water tubes are numbered 8 and the water space external to the compartment 2' is numbered 1'.

Since in the construction illustrated in Figure 4, a, single lower drum 9 is used, direct passage between the two sets of tubes 3' and 6 is screened at the two regions by the provision of baifie plates l0.

Above the open top of the compartments 2 or 2', may be arranged a suitable deflector I I shown in chain line, in order to deflect outwardly the uprising stream of steam with any admixture of Water so as to cause deposition of the water particles into the water space I or I.

It will be obvious that the compartment 2 or 2 can be constructed and secured in position in a variety of ways. For example the compartment may be built up and secured in position or formed of sections which are joined together after insertion through the usual manhole. The metal plates forming the compartment may be welded at their lower edges to the tube plate of the upper drum or may be securedin a watertight manner to angles or plating secured to the tube plate.

What I claim is:-

1. A water tube boiler including an upper drum and a lower drum connected by upcomer and downcomer tubes, characterized in that the upper "drum has a compartment at its bottom of such height as to extend near to or above the working level of water contained in the drum external to the compartment and adapted to exclude said water, the upcomer tubes are exposed to the region of highest temperature in the furnace and have their upper ends arranged to discharge directly into the bottom of said compartment, the compartment is of materially greater capacity than said tube ends and is wide open at its top for free escape into the upper drum of the fluid discharged by said upcomer tubes to thereby assist upward flow through the upcomer tubes, the downcomer tubes lead from the upper drum, at points external to said compartment and below the level of the top of the compartment, to the lower drum, and their total capacity exceeds that of the upcomer tubes, and a feed water delivery conduit opens into the upper drum external to the compartment and below the level of the top of the compartment and adjacent to the inlets of the downcomer tubes.

2. A water tube boiler including an upper drum and a lower drum connected by upcomer and downcomer tubes, characterized in that the upper drum has a compartment at its bottom of such height as to extend near to or above the working level of water contained in the drum external to the compartment and adapted to exclude said water, the upcomer tubes are exposed to the region of highest temperature in the furnace and have their upper ends arranged to discharge directly into the bottom of said compartment, the compartment is of materially greater capacity than said tube ends and is wide open at its top for free escape into the upper drum of the fluid discharged by said upcomer tubes to thereby assist upward flow through the upcomer tubes, the downcomer tubes lead from the upper drum, at points external to said compartment, to the lower drum, and a feed water delivery conduit opens into the upper drum external to the compartment and below the level of the top of the compartment and adjacent to the inlets of the downcomer tubes.

3. A water tube boiler according to claim 2, characterized in that there is a bafile within the lower drum to prevent direct flow through said drum from the delivery ends of the downcomer tubes to the receiving ends of the upcomer tubes.

4. A water tube boiler including an upper drum, and laterally spaced lower drums each connected to the upper drum by upcomer tubes and downcomer tubes, characterized in that the upper drum has at its bottom a compartment extending longitudinally thereof and medially disposed transversely of the drum to afford water spaces in the drum at opposite sides of the exterior of the compartment, and said compartment is of such height as to extend near to or above the working level of water contained in the drum external to the compartment and is adapted to exclude said Water, the upcomer tubes leading from both lower drums to the upper drum are exposed to the region of highest temperature in the furnace and have their upper ends arranged to discharge directly into the bottom of said compartment, the compartment is of materially greater capacity than said tube ends and is wide open at its top for free escape into the upper drum of the fluid discharged by the upcomer tubes to thereby assist upward flow through the upcomer tubes, the downcomer tubes lead from the water spaces in the upper drum at opposite sides of said compartment and diverge downward to the respective lower drums, and a feed water delivery conduit opens into the upper drum external to the compartment and below the level of the top of the compartment and adjacent to the inlets of the downcomer tubes.

' SYDNEY RUPERT DIGHT. 

